STX Rules and Setup Questions

[H1C]

Originally Posted by smg1138

What do you guys think about my new alignment? I was still getting noticeable outside tire wear at -2.5 Front -2 Rear so I decided to go all out. From what I've read these specs should give even wear and maximum grip. Will check with a pyrometer at next event to see if any tweaks are needed.

Your Firestone alignment is nearly identical to the one I got at my local Firestone -- I have 0.1 deg more camber front and rear. I still get a little more wear on the outside edge of my RE-71s in our local asphalt lot, but it's not as bad as it was at -3 or -2.5 deg. I think to get even wear I'd have to run -4 in front, -3 rear, but I'm not willing to do that because I still daily drive my car, and my street tires are wearing out considerably faster on the inside edge as it is. I was hoping not to have to flip the RE-71s at my current settings, but it looks like I'll have to at some point.



I also have the Ground Control camber plates and like them a lot. They're quiet, add bump travel, hold settings well, and they come with O-ring sealed radial bearing spring perches that you can take apart and clean and re-grease as needed. I'm not concerned with the minimal caster they can add: in fact I minimized the caster on them because I've found that with more caster, the inside rear tire tends to unload more, as you add more steering input.

[smg1138]

Originally Posted by H1C

I also have the Ground Control camber plates and like them a lot. They're quiet, add bump travel, hold settings well, and they come with O-ring sealed radial bearing spring perches that you can take apart and clean and re-grease as needed. I'm not concerned with the minimal caster they can add: in fact I minimized the caster on them because I've found that with more caster, the inside rear tire tends to unload more, as you add more steering input.

I'm more interested in evening out my caster than getting a ton. Just out of curiosity though, how much positive caster can you get out of them? I'm seriously considering the GC plates as they seem to offer a lot of value for the money.

[H1C]

Originally Posted by smg1138

I'm more interested in evening out my caster than getting a ton. Just out of curiosity though, how much positive caster can you get out of them? I'm seriously considering the GC plates as they seem to offer a lot of value for the money.

At their minimal settings, my caster is at 5.8 driver's side, 5.6 passenger. I think, but am not sure, that that's what my caster was with the OEM top hats. If they have 0.5 deg of adjustment as @AFRichZC6 said, you should be able to even yours out with them. But you'd have to raise the side at 5.6 to match the side at 5.9.



I wouldn't worry too much about the difference in caster that you have from side to side. I don't think I've ever owned a car that had perfectly matching caster from side to side. I would guess that a couple mm or less difference in how the shock mounting holes in the body line up to each other from side to side would account for 0.2 - 0.3 deg of difference in caster.

[H1C]

Originally Posted by smg1138

I'm more interested in evening out my caster than getting a ton. Just out of curiosity though, how much positive caster can you get out of them? I'm seriously considering the GC plates as they seem to offer a lot of value for the money.

I recommend also that you look into GC's rear top mounts, if they still make them. They add about an inch of bump travel in the rear, where our cars need it more than in the front.

[AFRichZC6]

I don't think you can get GC rear top mounts anymore, but DIF and Raceseng are a couple of good options.

Just checked my alignment specs. With GC camber plates, I get 6.0 and 6.2 degrees of caster, left and right.

I plotted the difference in camber gain from caster at various steering angles, and going from 6 degrees to 7 wasn't much. You'll be fine with either GC or Raceseng. I have a friend who has a set of Raceseng CasCam plates sitting around, and if you're interested, I can put you in contact with him.

[M0nk3y]

Originally Posted by AFRichZC6

I don't think you can get GC rear top mounts anymore, but DIF and Raceseng are a couple of good options.

Just checked my alignment specs. With GC camber plates, I get 6.0 and 6.2 degrees of caster, left and right.

I plotted the difference in camber gain from caster at various steering angles, and going from 6 degrees to 7 wasn't much. You'll be fine with either GC or Raceseng. I have a friend who has a set of Raceseng CasCam plates sitting around, and if you're interested, I can put you in contact with him.

I come from the world of BMWs, but typical convention was max out caster and then get your camber.

Also - I have a set of Diftech rear mounts that I have laying around if you're interested (for whoever was looking). They add additional travel in the rear

[AFRichZC6]

Originally Posted by M0nk3y

I come from the world of BMWs, but typical convention was max out caster and then get your camber.

I agree in getting as much caster as possible, and any amount gained is better than nothing gained at all. For this platform, you can only gain so much over stock through camber plates alone. My argument is you should try to get as much caster as you can, but don't fret if you can't squeeze out every bit of caster angle as possible.

I was once interested in switching my GC plates for another set of camber plates that got more caster, so I did some calculations on a change from 6 to 7 degrees of caster.

After you take into consideration how much camber is lost through kingpin inclination angle and included angle (I used 13.5 degrees for included angle), the net gain in camber at 90 degrees of steering input was only ~0.11 degrees more camber.

At 180 degrees of steering input, you get closer to ~0.24 degrees more camber, which would be seen in sharper turnaround elements. This amount would then be fairly useful.

I would argue the average steering input angle is no more than 120 degrees in autocross, at which you would get no more than ~0.16 degrees.

[smg1138]

Is there any downside to adding more caster? Think I remember reading somewhere that it can put more stress on the power steering rack. Anybody had issues with that?

[cjd]

Originally Posted by smg1138

Is there any downside to adding more caster? Think I remember reading somewhere that it can put more stress on the power steering rack. Anybody had issues with that?

I had power steering cut out in some circumstances on my '14. I had that a lot less when I switched to different setup with more caster... But less spring. YMMV. I run whatever extra my Raceseng cascams give me.

[H1C]

Originally Posted by smg1138

Is there any downside to adding more caster? Think I remember reading somewhere that it can put more stress on the power steering rack. Anybody had issues with that?

With the amount of additional caster you can get from camber plates, probably not. You'll get more dynamic camber as you steer, a stronger self-centering effect in the steering, and a slightly heavier steering feel.



I used to have adjustable front LCAs and experimented with caster settings up to 7.5 - 8 degrees. As you increase caster, you increase a jacking effect as you increase steering input -- the outside front corner will drop and the inside rear will lift. Go-kart racers use caster to lift the inside rear to be able to corner, since they don't have differentials:


https://www.paradigmshiftracing.com/...heeled-vehicle



6.5 - 7.5 deg of caster helped in tight corners, but I didn't like the effect in faster corners. Also, my power steering would cut out from time to time at 6.5 deg and above. Since I went back to factory caster settings, I haven't had the power steering cut out yet.



For auto-x, I prefer the lighter steering at the factory caster setting and the lessened jacking effect for faster corners and transitions, and would rather run more static camber instead. On the street, I liked the strong self-centering effect of higher caster settings.

[BR-ZED]

Originally Posted by H1C

Your Firestone alignment is nearly identical to the one I got at my local Firestone -- I have 0.1 deg more camber front and rear. I still get a little more wear on the outside edge of my RE-71s in our local asphalt lot, but it's not as bad as it was at -3 or -2.5 deg. I think to get even wear I'd have to run -4 in front, -3 rear, but I'm not willing to do that because I still daily drive my car, and my street tires are wearing out considerably faster on the inside edge as it is. I was hoping not to have to flip the RE-71s at my current settings, but it looks like I'll have to at some point.



I also have the Ground Control camber plates and like them a lot. They're quiet, add bump travel, hold settings well, and they come with O-ring sealed radial bearing spring perches that you can take apart and clean and re-grease as needed. I'm not concerned with the minimal caster they can add: in fact I minimized the caster on them because I've found that with more caster, the inside rear tire tends to unload more, as you add more steering input.

Looking at your specs, that's exactly what I asked my shop to do. Despite that, this is what I got:


The handwritten numbers are the numbers with the driver in the car. So even side to side.

This is with a slotted coilover strut hole and camber plates. No camber bolts. I had some SPC bolts but they didn't want to install them as they said they would likely slip.

Not sure why they put so much camber in the rear (I had asked for 1 degree less in the rear) but they insisted this would be a well balanced setup, and that 3.5 degrees was too much for tires if daily driving (which I sort of do - 4 days a week or so in the summers only). So kind of mixed feelings. What do people think? I don't see many square setups camber wise for STX.

And on another note - what is a good starting point for hankook rs4 in 255/40? I was reading 38, but that seemed high (especially because I ran 32/30 on my 225/45/17 RE71Rs in CS/DS).

[cjd]

Originally Posted by BR-ZED

Looking at your specs, that's exactly what I asked my shop to do. Despite that, this is what I got:


The handwritten numbers are the numbers with the driver in the car. So even side to side.

This is with a slotted coilover strut hole and camber plates. No camber bolts. I had some SPC bolts but they didn't want to install them as they said they would likely slip.

Not sure why they put so much camber in the rear (I had asked for 1 degree less in the rear) but they insisted this would be a well balanced setup, and that 3.5 degrees was too much for tires if daily driving (which I sort of do - 4 days a week or so in the summers only). So kind of mixed feelings. What do people think? I don't see many square setups camber wise for STX.

And on another note - what is a good starting point for hankook rs4 in 255/40? I was reading 38, but that seemed high (especially because I ran 32/30 on my 225/45/17 RE71Rs in CS/DS).

They're idiots. That's not remotely balanced and sure... Daily use may wear out in 30k instead of 25k, but autox will be done after 80 runs, not 150 or more. You'll burn race tires to save a bit on the daily? I ran -2.8r and it was a bit much. -3.5/-2.5 and I easily go 200+ runs on a set of tires...RE71s are starting to play hockey puck. Not even close to going through a set of PSS on the highway, 14k so far on them.


Sorry to be negative. I'm exaggerating wear at -2.9f, it'll be pretty good. But they didn't do as you asked, and I'm pretty sure you'd have been happier with the results if they had.

[BR-ZED]

I'm a little confused by your response... are you saying my settings (2.9/2.8) will go through tires faster in autocross than 3.5/2.5 would?

I put about 5k or less on the car per year, so I would expect autocross to kill my tires before daily driving. I mentioned to them I wanted 0 toe since i do drive it on the road so that's probably why they changed my camber settings...

[cjd]

Originally Posted by BR-ZED

I'm a little confused by your response... are you saying my settings (2.9/2.8) will go through tires faster in autocross than 3.5/2.5 would?

I put about 5k or less on the car per year, so I would expect autocross to kill my tires before daily driving. I mentioned to them I wanted 0 toe since i do drive it on the road so that's probably why they changed my camber settings...

Well, sorta, yeah, but nowhere near as fast as I suggest, and I tried to say I was being dramatic/exaggerating but ended up being confusing I guess. I've averaged 6k every summer to get the 14k on the PSS. The rubber will probably be done before I got the wear bars, honestly.


You would have been fine with the settings you asked for on the street, and slightly faster on course. Drive it, see how it feels, watch temps, all that stuff. Change it some other day.